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Mondal A, Bhattacharya A, Singh V, Pandita S, Bacolla A, Pandita RK, Tainer JA, Ramos KS, Pandita TK, Das C. Stress Responses as Master Keys to Epigenomic Changes in Transcriptome and Metabolome for Cancer Etiology and Therapeutics. Mol Cell Biol 2022; 42:e0048321. [PMID: 34748401 PMCID: PMC8773053 DOI: 10.1128/mcb.00483-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
From initiation through progression, cancer cells are subjected to a magnitude of endogenous and exogenous stresses, which aid in their neoplastic transformation. Exposure to these classes of stress induces imbalance in cellular homeostasis and, in response, cancer cells employ informative adaptive mechanisms to rebalance biochemical processes that facilitate survival and maintain their existence. Different kinds of stress stimuli trigger epigenetic alterations in cancer cells, which leads to changes in their transcriptome and metabolome, ultimately resulting in suppression of growth inhibition or induction of apoptosis. Whether cancer cells show a protective response to stress or succumb to cell death depends on the type of stress and duration of exposure. A thorough understanding of epigenetic and molecular architecture of cancer cell stress response pathways can unveil a plethora of information required to develop novel anticancer therapeutics. The present view highlights current knowledge about alterations in epigenome and transcriptome of cancer cells as a consequence of exposure to different physicochemical stressful stimuli such as reactive oxygen species (ROS), hypoxia, radiation, hyperthermia, genotoxic agents, and nutrient deprivation. Currently, an anticancer treatment scenario involving the imposition of stress to target cancer cells is gaining traction to augment or even replace conventional therapeutic regimens. Therefore, a comprehensive understanding of stress response pathways is crucial for devising and implementing novel therapeutic strategies.
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Affiliation(s)
- Atanu Mondal
- Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
- Homi Bhaba National Institute, Mumbai, India
| | - Apoorva Bhattacharya
- Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
| | - Vipin Singh
- Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
- Homi Bhaba National Institute, Mumbai, India
| | - Shruti Pandita
- Division of Hematology and Medical Oncology, St. Louis University, St. Louis, Missouri, USA
| | - Albino Bacolla
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA
| | - Raj K. Pandita
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA
| | - John A. Tainer
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA
| | - Kenneth S. Ramos
- Center for Genomics and Precision Medicine, Texas A&M College of Medicine, Houston, Texas, USA
| | - Tej K. Pandita
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA
- Center for Genomics and Precision Medicine, Texas A&M College of Medicine, Houston, Texas, USA
| | - Chandrima Das
- Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
- Homi Bhaba National Institute, Mumbai, India
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Ihara M, Shichijo K, Ashizawa K, Matsuda K, Otsubo R, Horie I, Nakashima M, Kudo T. Relationship between thyroid tumor radiosensitivity and nuclear localization of DNA-dependent protein kinase catalytic subunit. JOURNAL OF RADIATION RESEARCH 2020; 61:511-516. [PMID: 32567663 PMCID: PMC7336817 DOI: 10.1093/jrr/rraa032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/10/2020] [Indexed: 06/11/2023]
Abstract
Thyroid tumors are the most common types of endocrine malignancies and are commonly treated with radioactive iodine (RAI) to destroy remaining cancer cells following surgical intervention. We previously reported that the expression levels of double-stranded DNA-dependent protein kinase catalytic subunit (DNA-PKcs), which plays a key role in non-homologous end joining, are correlated with the radiosensitivity of cancer cells. Specifically, cells expressing high levels of DNA-PKcs exhibited radiation resistance, whereas cells expressing low levels were sensitive to radiation treatment. In this study, we observed full-length native DNA-PKcs (460 kDa) in radiation-resistant FRO and KTC-2 cells through western blot analysis using an antibody against the C-terminus of DNA-PKcs. In contrast, cleaved DNA-PKcs (175 kDa) were observed in radiation-sensitive TPC-1 and KTC-1 cells. Almost equal amounts of DNA-PKcs were observed in moderately radiation-sensitive WRO cells. We also describe a simple method for the prediction of radiation therapy efficacy in individual cases of thyroid cancers based on staining for DNA-PKcs in human cancer cell lines. Immunofluorescent staining showed that native DNA-PKcs was localized largely in the cytoplasm and only rarely localized in the nuclei of radiation-resistant thyroid cancer cells, whereas in radiation-sensitive cancer cells a 175-kDa cleaved C-terminal fragment of DNA-PKcs was localized mainly inside the nuclei. Therefore, DNA-PKcs moved to the nucleus after γ-ray irradiation. Our results suggest a new method for classifying human thyroid tumors based on their cellular distribution patterns of DNA-PKcs in combination with their radiosensitivity.
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Affiliation(s)
- Makoto Ihara
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Kazuko Shichijo
- Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Kiyoto Ashizawa
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Katsuya Matsuda
- Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Ryota Otsubo
- Department of Surgical Oncology, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan
| | - Ichiro Horie
- Department of Endocrinology and Metabolism, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan
| | - Masahiro Nakashima
- Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Takashi Kudo
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
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Ihara M, Shichijo K, Kudo T, Ohtsuka K. Reactivation of heat-inactivated Ku proteins by heat shock cognate protein HSC73. Int J Hyperthermia 2019; 36:438-443. [PMID: 30922135 DOI: 10.1080/02656736.2019.1587009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
PURPOSE Mouse double-stranded DNA-dependent protein kinase (DNA-PK) activity is heat sensitive. Recovery of heat-inactivated DNA repair activity is a problem after combination therapy with radiation and heat. We investigated the mechanism of recovery of heat-inactivated DNA-PK activity. METHODS Hybrid cells containing a fragment of human chromosome 8 in scid cells (RD13B2) were used. DNA-PK activity was measured by an in vitro assay. Immunoprecipitation of the nuclear extract was performed with an anti-Ku80 antibody. Proteins co-precipitated with Ku80 were separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and detected by Western blotting using anti-heat shock protein (HSP)72 and anti-heat shock cognate protein (HSC)73 antibodies. HSC73 was overexpressed with the pcDNA3.1 vector. Short hairpin (sh)RNA was used to downregulate HSC73 and HSP72. RESULTS The activity of heat-inactivated DNA-PK recovered to about 50% of control during an additional incubation at 37 °C after heat treatment at 44 °C for 15 min in the presence of cycloheximide (which inhibits de novo protein synthesis). Maximal recovery was observed within 3 h of incubation at 37 °C after heat treatment. Constitutively expressed HSC73, which folds newly synthesized proteins, reached maximal levels 3 h after heat treatment using a co-immunoprecipitation assay with the Ku80 protein. Inhibiting HSC73, but not HSP72, expression with shRNA decreased the recovery of DNA-PK activity after heat treatment. CONCLUSIONS These results suggest that de novo protein synthesis is unnecessary for recovery of some heat-inactivated DNA-PK. Rather, it might be reactivated by the molecular chaperone activity of HSC73, but not HSP72.
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Affiliation(s)
- Makoto Ihara
- a Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute , Nagasaki University , Nagasaki , Japan
| | - Kazuko Shichijo
- b Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute , Nagasaki University , Nagasaki , Japan
| | - Takashi Kudo
- a Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute , Nagasaki University , Nagasaki , Japan
| | - Kenzo Ohtsuka
- c Laboratory of Cell and Stress Biology, College of Bioscience and Biotechnology , Chubu University , Kasugai , Japan
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Ihara M, Ashizawa K, Shichijo K, Kudo T. Expression of the DNA-dependent protein kinase catalytic subunit is associated with the radiosensitivity of human thyroid cancer cell lines. JOURNAL OF RADIATION RESEARCH 2019; 60:171-177. [PMID: 30476230 PMCID: PMC6430255 DOI: 10.1093/jrr/rry097] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 09/13/2018] [Indexed: 05/02/2023]
Abstract
The prognosis and treatment of thyroid cancer depends on the type and stage of the disease. Radiosensitivity differs among cancer cells owing to their varying capacity for repair after irradiation. Radioactive iodine can be used to destroy thyroid cancer cells. However, patient prognosis and improvement after irradiation varies. Therefore, predictive measures are important for avoiding unnecessary exposure to radiation. We describe a new method for predicting the effects of radiation in individual cases of thyroid cancer based on the DNA-dependent protein kinase (DNA-PK) activity level in cancer cells. The radiation sensitivity, DNA-PK activity, and cellular levels of DNA-PK complex subunits in five human thyroid cancer cell lines were analyzed in vitro. A positive correlation was observed between the D10 value (radiation dose that led to 10% survival) of cells and DNA-PK activity. This correlation was not observed after treatment with NU7441, a DNA-PK-specific inhibitor. A significant correlation was also observed between DNA-PK activity and expression levels of the DNA-PK catalytic subunit (DNA-PKcs). Cells expressing low DNA-PKcs levels were radiation-sensitive, and cells expressing high DNA-PKcs levels were radiation-resistant. Our results indicate that radiosensitivity depends on the expression level of DNA-PKcs in thyroid cancer cell lines. Thus, the DNA-PKcs expression level is a potential predictive marker of the success of radiation therapy for thyroid tumors.
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Affiliation(s)
- Makoto Ihara
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki, Japan
- Corresponding author. Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki 852-8523, Japan. Tel: +81-95-819-71013; Fax: +81-95-849-7104;
| | - Kiyoto Ashizawa
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki, Japan
| | - Kazuko Shichijo
- Department of Tumor and Diagnostic Pathology, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki, Japan
| | - Takashi Kudo
- Department of Radioisotope Medicine, Atomic Bomb Disease and Hibakusha Medicine Unit, Atomic Bomb Disease Institute Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki, Japan
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Nakagawa Y, Kajihara A, Takahashi A, Murata AS, Matsubayashi M, Ito SS, Ota I, Nakagawa T, Hasegawa M, Kirita T, Ohnishi T, Mori E. BRCA2 protects mammalian cells from heat shock. Int J Hyperthermia 2017; 34:795-801. [PMID: 28891354 DOI: 10.1080/02656736.2017.1370558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
PURPOSE Heat shock induces DNA double-strand breaks (DSBs) in mammalian cells. Mammalian cells are capable of repairing DSBs by utilising the homologous recombination (HR) pathway. Breast cancer susceptibility gene 2 (BRCA2) is known to regulate the HR pathway. Here, we investigate the role of BRCA2 in repairing DNA damage induced by heat shock. MATERIALS AND METHODS Chinese hamster lung fibroblast cell lines and human tongue squamous cell carcinoma SAS cells were used. RAD51 foci formation assay was used as an HR indicator. Heat sensitivity was analysed with colony forming assays. Phosphorylated histone H2AX (γH2AX) intensity, which correlates with the number of DSBs, was analysed with flow cytometry. RESULTS RAD51 foci appeared with heat shock, and the number of cells with RAD51 foci was maximal at about 4 h after heat shock. Heat-induced RAD51 foci co-localised with γH2AX foci. BRCA2-deficient cells were sensitive to heat when compared to their parental wild-type cells. Heat-induced γH2AX was higher in BRCA2-deficient cells compared to parental cells. In SAS cells, cells transfected with BRCA2-siRNA were more sensitive to heat than cells transfected with negative control siRNA. Apoptotic bodies increased in number more rapidly in BRCA2-siRNA transfected cells than in cells transfected with negative control siRNA when cells were observed at 48 h after a heat treatment. In addition, cells deficient in BRCA2 were incapable of activating heat-induced G2/M arrest. CONCLUSION BRCA2 has a protecting role against heat-induced cell death. BRCA2 might be a potential molecular target for hyperthermic cancer therapy.
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Affiliation(s)
- Yosuke Nakagawa
- a Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara , Japan
| | - Atsuhisa Kajihara
- a Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara , Japan
| | | | - Akiho S Murata
- c Department of Future Basic Medicine , Nara Medical University , Nara , Japan
| | - Masaya Matsubayashi
- c Department of Future Basic Medicine , Nara Medical University , Nara , Japan
| | - Soichiro S Ito
- a Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara , Japan
| | - Ichiro Ota
- d Department of Otolaryngology - Head and Neck Surgery , Nara Medical University , Nara , Japan
| | - Takahiko Nakagawa
- c Department of Future Basic Medicine , Nara Medical University , Nara , Japan
| | - Masatoshi Hasegawa
- e Department of Radiation Oncology , Nara Medical University , Nara , Japan
| | - Tadaaki Kirita
- a Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara , Japan
| | - Takeo Ohnishi
- e Department of Radiation Oncology , Nara Medical University , Nara , Japan
| | - Eiichiro Mori
- c Department of Future Basic Medicine , Nara Medical University , Nara , Japan
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Peeken JC, Vaupel P, Combs SE. Integrating Hyperthermia into Modern Radiation Oncology: What Evidence Is Necessary? Front Oncol 2017; 7:132. [PMID: 28713771 PMCID: PMC5492395 DOI: 10.3389/fonc.2017.00132] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/06/2017] [Indexed: 12/13/2022] Open
Abstract
Hyperthermia (HT) is one of the hot topics that have been discussed over decades. However, it never made its way into primetime. The basic biological rationale of heat to enhance the effect of radiation, chemotherapeutic agents, and immunotherapy is evident. Preclinical work has confirmed this effect. HT may trigger changes in perfusion and oxygenation as well as inhibition of DNA repair mechanisms. Moreover, there is evidence for immune stimulation and the induction of systemic immune responses. Despite the increasing number of solid clinical studies, only few centers have included this adjuvant treatment into their repertoire. Over the years, abundant prospective and randomized clinical data have emerged demonstrating a clear benefit of combined HT and radiotherapy for multiple entities such as superficial breast cancer recurrences, cervix carcinoma, or cancers of the head and neck. Regarding less investigated indications, the existing data are promising and more clinical trials are currently recruiting patients. How do we proceed from here? Preclinical evidence is present. Multiple indications benefit from additional HT in the clinical setting. This article summarizes the present evidence and develops ideas for future research.
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Affiliation(s)
- Jan C Peeken
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, München, Germany
| | - Peter Vaupel
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, München, Germany
| | - Stephanie E Combs
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, München, Germany.,Department of Radiation Sciences (DRS), Institute of Innovative Radiotherapy (iRT), Helmholtz Zentrum München, Neuherberg, Germany
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Takahashi A, Mori E, Nakagawa Y, Kajihara A, Kirita T, Pittman DL, Hasegawa M, Ohnishi T. Homologous recombination preferentially repairs heat-induced DNA double-strand breaks in mammalian cells. Int J Hyperthermia 2016; 33:336-342. [PMID: 27776457 DOI: 10.1080/02656736.2016.1252989] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PURPOSE Heat shock induces DNA double-strand breaks (DSBs), but the precise mechanism of repairing heat-induced damage is unclear. Here, we investigated the DNA repair pathways involved in cell death induced by heat shock. MATERIALS AND METHODS B02, a specific inhibitor of human RAD51 (homologous recombination; HR), and NU7026, a specific inhibitor of DNA-PK (non-homologous end-joining; NHEJ), were used for survival assays of human cancer cell lines with different p53-gene status. Mouse embryonic fibroblasts (MEFs) lacking Lig4 (NHEJ) and/or Rad54 (HR) were used for survival assays and a phosphorylated histone H2AX at Ser139 (γH2AX) assay. MEFs lacking Rad51d (HR) were used for survival assays. SPD8 cells were used to measure HR frequency after heat shock. RESULTS Human cancer cells were more sensitive to heat shock in the presence of B02 despite their p53-gene status, and the effect of B02 on heat sensitivity was specific to the G2 phase. Rad54-deficient MEFs were sensitive to heat shock and showed prolonged γH2AX signals following heat shock. Rad51d-deficient MEFs were also sensitive to heat shock. Moreover, heat shock-stimulated cells had increased HR. CONCLUSIONS The HR pathway plays an important role in the survival of mammalian cells against death induced by heat shock via the repair of heat-induced DNA DSBs.
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Affiliation(s)
| | - Eiichiro Mori
- b Department of Radiation Oncology , Nara Medical University , Nara, Japan
| | - Yosuke Nakagawa
- c Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara, Japan
| | - Atsuhisa Kajihara
- c Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara, Japan
| | - Tadaaki Kirita
- c Department of Oral and Maxillofacial Surgery , Nara Medical University , Nara, Japan
| | - Douglas L Pittman
- d Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy , University of South Carolina , Columbia , SC , USA
| | - Masatoshi Hasegawa
- b Department of Radiation Oncology , Nara Medical University , Nara, Japan
| | - Takeo Ohnishi
- b Department of Radiation Oncology , Nara Medical University , Nara, Japan
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Oei AL, Vriend LEM, Crezee J, Franken NAP, Krawczyk PM. Effects of hyperthermia on DNA repair pathways: one treatment to inhibit them all. Radiat Oncol 2015; 10:165. [PMID: 26245485 PMCID: PMC4554295 DOI: 10.1186/s13014-015-0462-0] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/13/2015] [Indexed: 12/03/2022] Open
Abstract
The currently available arsenal of anticancer modalities includes many DNA damaging agents that can kill malignant cells. However, efficient DNA repair mechanisms protect both healthy and cancer cells against the effects of treatment and contribute to the development of drug resistance. Therefore, anti-cancer treatments based on inflicting DNA damage can benefit from inhibition of DNA repair. Hyperthermia – treatment at elevated temperature – considerably affects DNA repair, among other cellular processes, and can thus sensitize (cancer) cells to DNA damaging agents. This effect has been known and clinically applied for many decades, but how heat inhibits DNA repair and which pathways are targeted has not been fully elucidated. In this review we attempt to summarize the known effects of hyperthermia on DNA repair pathways relevant in clinical treatment of cancer. Furthermore, we outline the relationships between the effects of heat on DNA repair and sensitization of cells to various DNA damaging agents.
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Affiliation(s)
- Arlene L Oei
- Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands. .,Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Lianne E M Vriend
- Van Leeuwenhoek Centre for Advanced Microscopy (LCAM)-AMC, Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
| | - Johannes Crezee
- Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Nicolaas A P Franken
- Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands. .,Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Przemek M Krawczyk
- Van Leeuwenhoek Centre for Advanced Microscopy (LCAM)-AMC, Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
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Ihara M, Takeshita S, Okaichi K, Okumura Y, Ohnishi T. Heat exposure enhances radiosensitivity by depressing DNA-PK kinase activity during double strand break repair. Int J Hyperthermia 2014; 30:102-9. [DOI: 10.3109/02656736.2014.887793] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Tomita M. Involvement of DNA-PK and ATM in radiation- and heat-induced DNA damage recognition and apoptotic cell death. JOURNAL OF RADIATION RESEARCH 2010; 51:493-501. [PMID: 20814172 DOI: 10.1269/jrr.10039] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Exposure to ionizing radiation and hyperthermia results in important biological consequences, e.g. cell death, chromosomal aberrations, mutations, and DNA strand breaks. There is good evidence that the nucleus, specifically cellular DNA, is the principal target for radiation-induced cell lethality. DNA double-strand breaks (DSBs) are considered to be the most serious type of DNA damage induced by ionizing radiation. On the other hand, verifiable mechanisms which can lead to heat-induced cell death are damage to the plasma membrane and/or inactivation of heat-labile proteins caused by protein denaturation and subsequent aggregation. Recently, several reports have suggested that DSBs can be induced after hyperthermia because heat-induced phosphorylated histone H2AX (γ-H2AX) foci formation can be observed in several mammalian cell lines. In mammalian cells, DSBs are repaired primarily through two distinct and complementary mechanisms: non-homologous end joining (NHEJ), and homologous recombination (HR) or homology-directed repair (HDR). DNA-dependent protein kinase (DNA-PK) and ataxia-telangiectasia mutated (ATM) are key players in the initiation of DSB repair and phosphorylate and/or activate many substrates, including themselves. These phosphorylated substrates have important roles in the functioning of cell cycle checkpoints and in cell death, as well as in DSB repair. Apoptotic cell death is a crucial cell suicide mechanism during development and in the defense of homeostasis. If DSBs are unrepaired or misrepaired, apoptosis is a very important system which can protect an organism against carcinogenesis. This paper reviews recently obtained results and current topics concerning the role of DNA-PK and ATM in heat- or radiation-induced apoptotic cell death.
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Affiliation(s)
- Masanori Tomita
- Department of Radiation Oncology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
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11
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Takahashi A, Mori E, Somakos GI, Ohnishi K, Ohnishi T. Heat induces gammaH2AX foci formation in mammalian cells. Mutat Res 2008; 656:88-92. [PMID: 18765297 DOI: 10.1016/j.mrgentox.2008.07.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2008] [Revised: 06/13/2008] [Accepted: 07/26/2008] [Indexed: 11/29/2022]
Abstract
H2AX is a histone variant which is present and ubiquitously distributed throughout the genome. An immunocytochemical assay using antibodies capable of recognizing histone H2AX phosphorylated at serine 139 (gammaH2AX) is very sensitive and is a specific indicator for the existence of a DNA double strand break. Although heat stress has been reported to induce the formation of gammaH2AX foci, no gammaH2AX foci formation was observed in several mammalian cell lines after heat shock. Since this was in contrast to earlier reports, the work described here was intended to verify that heat-induced gammaH2AX foci do form in mammalian cell lines other than the cell lines used in earlier reports concerning gammaH2AX foci formation. The cell lines used in this work includes cell lines with differing p53-gene status (H1299, H1299/neo, H1299/mp53 and H1299/wtp53 cells), various cancer cell lines (HeLa, HepG2, U2-OS cells), normal human cells (HEK-293 and AG1522), and cell lines established from other species (MEF normal mouse cells and CHL normal Chinese hamster cells). Exponentially growing cells were exposed to heat shock (42 degrees C for 6 h or 45.5 degrees C for 20 min) or to X-rays (3Gy). The presence of gammaH2AX was examined with immunocytochemistry and flow cytometry. Induction of gammaH2AX foci formation was observed in all of the mammalian cell lines used here after heat-treatment as well as after X-irradiation. However, the intensity of gammaH2AX was different in the different cell lines used. These results confirm that heat can induce gammaH2AX foci formation in many mammalian cell lines.
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Affiliation(s)
- Akihisa Takahashi
- Department of Biology, School of Medicine, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan
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Ricci F, Pucci S, Sesti F, Missiroli F, Cerulli L, Spagnoli LG. Modulation of Ku70/80, Clusterin/ApoJ Isoforms and Bax Expression in Indocyanine-Green-Mediated Photo-Oxidative Cell Damage. Ophthalmic Res 2007; 39:164-73. [PMID: 17534116 DOI: 10.1159/000103236] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Accepted: 12/18/2006] [Indexed: 11/19/2022]
Abstract
PURPOSE In order to characterize the biological effects and molecular mechanism underlying indocyanine-green (ICG)-mediated photo-oxidative cell damage, human cultured retinal pigmented epithelium (RPE) cells preloaded with ICG were exposed to 810-nm laser irradiation. Cell viability and death induction were examined, as well as the modulation of proteins involved in cell death and DNA repair. METHODS ARPE-19 cells preloaded with 100 microM ICG were irradiated using continuous and micropulsed 810-nm laser for the dye photoactivation, and cell viability and apoptosis were evaluated. The expression and subcellular localization of Bax, Ku70, Ku80 and clusterin/ApoJ were analyzed by immunocytochemistry and Western blot. RESULTS ICG photoactivation induced apoptosis in RPE cells. The micropulsed laser irradiation induced a higher percentage of cell killing as compared to continuous wave. Cell killing was inhibited by sodium azide, suggesting the involvement of reactive oxygen species in the laser-induced cell damage. Bax was strongly induced after 4 and up to 24 h of treatment. The nuclear proapoptotic isoform of clusterin/ApoJ was selectively upregulated after 24 h of treatment. The DNA repair machinery was upregulated after 4 and up to 24 h. CONCLUSION These data elucidate some molecular mechanisms involved in cell death induced by ICG photosensitization. The increase and relocalization of Bax into the mitochondria and the upregulation and translocation of the proapoptotic isoform of clusterin/ApoJ in the nucleus demonstrated the involvement of these proteins in the photo-oxidative cell death pathway. These data point out new molecular targets and suggest potential applications in the therapy of the retinal diseases that could benefit by selective RPE treatment.
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Affiliation(s)
- Federico Ricci
- Section of Ophthalmology, University of Rome Tor Vergata, Rome, Italy
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TAKAHASHI AKIHISA, OHNISHI TAKEO. What is the Critical Hyperthermia Target in Cancer Cells? ACTA ACUST UNITED AC 2006. [DOI: 10.3191/thermalmedicine.22.229] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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14
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Pajonk F, van Ophoven A, Weissenberger C, McBride WH. The proteasome inhibitor MG-132 sensitizes PC-3 prostate cancer cells to ionizing radiation by a DNA-PK-independent mechanism. BMC Cancer 2005; 5:76. [PMID: 16001975 PMCID: PMC1177933 DOI: 10.1186/1471-2407-5-76] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Accepted: 07/07/2005] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND By modulating the expression levels of specific signal transduction molecules, the 26S proteasome plays a central role in determining cell cycle progression or arrest and cell survival or death in response to stress stimuli, including ionizing radiation. Inhibition of proteasome function by specific drugs results in cell cycle arrest, apoptosis and radiosensitization of many cancer cell lines. This study investigates whether there is also a concomitant increase in cellular radiosensitivity if proteasome inhibition occurs only transiently before radiation. Further, since proteasome inhibition has been shown to activate caspase-3, which is involved in apoptosis, and caspase-3 can cleave DNA-PKcs, which is involved in DNA-double strand repair, the hypothesis was tested that caspase-3 activation was essential for both apoptosis and radiosensitization following proteasome inhibition. METHODS Prostate carcinoma PC-3 cells were treated with the reversible proteasome inhibitor MG-132. Cell cycle distribution, apoptosis, caspase-3 activity, DNA-PKcs protein levels and DNA-PK activity were monitored. Radiosensitivity was assessed using a clonogenic assay. RESULTS Inhibition of proteasome function caused cell cycle arrest and apoptosis but this did not involve early activation of caspase-3. Short-time inhibition of proteasome function also caused radiosensitization but this did not involve a decrease in DNA-PKcs protein levels or DNA-PK activity. CONCLUSION We conclude that caspase-dependent cleavage of DNA-PKcs during apoptosis does not contribute to the radiosensitizing effects of MG-132.
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Affiliation(s)
- Frank Pajonk
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA90095-1714, USA
| | - Arndt van Ophoven
- Department of Urology, University Hospital Münster, Albert-Schweitzer-Straße 33, D-48149 Münster Germany
| | - Christian Weissenberger
- Department of Radiation Oncology, University Hospital Freiburg, Robert-Koch-Straße 3, D-79106 Freiburg, Germany
| | - William H McBride
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA90095-1714, USA
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Kaneko H, Igarashi K, Kataoka K, Miura M. Heat shock induces phosphorylation of histone H2AX in mammalian cells. Biochem Biophys Res Commun 2005; 328:1101-6. [PMID: 15707990 DOI: 10.1016/j.bbrc.2005.01.073] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Indexed: 11/28/2022]
Abstract
Heat shock induces a variety of biological events including gene activation, cell cycle arrest, and apoptosis. Heat shock has recently been shown to be potentially useful when combined with radiation in cancer therapy, probably because, in mammalian cells, heat inhibits the repair of double-strand breaks (DSBs) induced by ionizing radiation. It remains unclear, however, whether heat shock by itself induces DSBs. In this communication, we present the first evidence that heat shock induces the phosphorylated form of histone H2AX, which is thought to be generated at the chromatin proximal to DSB sites. These results suggest that heat shock induces DSBs in mammalian cells and may provide direct evidence to explain previous reports on DSB-related events occurring after heat shock treatment.
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Affiliation(s)
- Haruna Kaneko
- Molecular Diagnosis and Therapeutics, Department of Oral Restitution, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan
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Yin HL, Suzuki Y, Matsumoto Y, Tomita M, Furusawa Y, Enomoto A, Morita A, Aoki M, Yatagai F, Suzuki T, Hosoi Y, Ohtomo K, Suzuki N. Radiosensitization by hyperthermia in the chicken B-lymphocyte cell line DT40 and its derivatives lacking nonhomologous end joining and/or homologous recombination pathways of DNA double-strand break repair. Radiat Res 2004; 162:433-41. [PMID: 15447039 DOI: 10.1667/rr3239] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Hyperthermia has a radiosensitizing effect, which is one of the most important biological bases for its use in cancer therapy with radiation. Although the mechanism of this effect has not been clarified in molecular terms, possible involvement of either one or both of two major DNA double-strand break (DSB) repair pathways, i.e. nonhomologous end joining (NHEJ) and homologous recombination (HR), has been speculated. To test this possibility, we examined cells of the chicken B-lymphocyte cell line DT40 and its derivatives lacking NHEJ and/or HR: KU70(-/-), DNA-PKcs(-/-/-), RAD54(-/-) and KU70(-/-)/RAD54(-/-). Radiosensitization by hyperthermia could be seen in all of the mutants, including KU70(-/-)/RAD54(-/-), which lacked both NHEJ and HR. Therefore, radiosensitization by hyperthermia cannot be explained simply by its inhibitory effects, if any, on NHEJ and/or HR alone. However, in NHEJ-defective KU70(-/-) and DNA-PKcs(-/-/-), consisting of two subpopulations with distinct radiosensitivity, the radiosensitive subpopulation, which is considered to be cells in G(1) and early S, was not sensitized. Substantial sensitization was seen only in the radioresistant subpopulation, which is considered to be cells in late S and G(2), capable of repairing DSBs through HR. This observation did not exclude possible involvement of NHEJ in G(1) and early S phase and also suggested inhibitory effects of hyperthermia on HR. Thus partial contribution of NHEJ and HR in radiosensitization by hyperthermia, especially that depending on the cell cycle stage, remains to be considered.
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Affiliation(s)
- Hong Lan Yin
- Department of Radiation Research, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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17
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Seno JD, Dynlacht JR. Intracellular redistribution and modification of proteins of the Mre11/Rad50/Nbs1 DNA repair complex following irradiation and heat-shock. J Cell Physiol 2004; 199:157-70. [PMID: 15039997 DOI: 10.1002/jcp.10475] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mre11, Rad50, and Nbs1form a tight complex which is homogeneously distributed throughout the nuclei of mammalian cells. However, after irradiation, the Mre11/Rad50/Nbs1 (M/R/N) complex rapidly migrates to sites of double strand breaks (DSBs), forming foci which remain until DSB repair is complete. Mre11 and Rad50 play direct roles in DSB repair, while Nbs1 appears to be involved in damage signaling. Hyperthermia sensitizes mammalian cells to ionizing radiation. Radiosensitization by heat shock is believed to be mediated by an inhibition of DSB repair. While the mechanism of inhibition of repair by heat shock remains to be elucidated, recent reports suggest that the M/R/N complex may be a target for inhibition of DSB repair and radiosensitization by heat. We now demonstrate that when human U-1 melanoma cells are heated at 42.5 or 45.5 degrees C, Mre11, Rad50, and Nbs1 are rapidly translocated from the nucleus to the cytoplasm. Interestingly, when cells were exposed to ionizing radiation (12 Gy of X-rays) prior to heat treatment, the extent and kinetics of translocation were increased when nuclear and cytoplasmic fractions of protein were analyzed immediately after treatment. The kinetics of the translocation and subsequent relocalization back into the nucleus when cells were incubated at 37 degrees C from 30 min to 7 h following treatment were different for each protein, which suggests that the proteins redistribute independently. However, a significant fraction of the translocated proteins exist as a triple complex in the cytoplasm. Treatment with leptomycin B (LMB) inhibits the translocation of Mre11, Rad50, and Nbs1 to the cytoplasm, leading us to speculate that the relocalization of the proteins to the cytoplasm occurs via CRM1-mediated nuclear export. In addition, while Nbs1 is rapidly phosphorylated in the nuclei of irradiated cells and is critical for a normal DNA damage response, we have found that Nbs1 is rapidly phosphorylated in the cytoplasm, but not in the nucleus, of heated irradiated cells. The phosphorylation of cytoplasmic Nbs1, which cannot be inhibited by wortmannin, appears to be a unique post-translational modification in heated, irradiated cells, and coupled with our novel observations that Mre11, Rad50, and Nbs1 translocate to the cytoplasm, lend further support for a role of the M/R/N complex in thermal radiosensitization and inhibition of DSB repair.
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Affiliation(s)
- Joshua D Seno
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis 46202, USA
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18
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Dynlacht JR, Bittner ME, Bethel JA, Beck BD. The non-homologous end-joining pathway is not involved in the radiosensitization of mammalian cells by heat shock. J Cell Physiol 2003; 196:557-64. [PMID: 12891712 DOI: 10.1002/jcp.10334] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A synergistic increase in cell killing is observed when a heat-shock is administered prior to, during, or immediately after exposure to ionizing radiation (IR). This phenomenon, known as heat-radiosensitization, is believed to be mediated by inhibition of repair of radiation-induced double strand breaks (DSB) when cells are exposed to temperatures above 42 degrees C. However, the mechanism by which heat inhibits DSB repair is unclear. The bulk of radiation-induced DSBs are repaired via the non-homologous end-joining pathway (NHEJ). Several reports indicate that the Ku70 and Ku80 subunits of the mammalian DNA-dependent protein kinase (DNA-PK), a complex involved in NHEJ, appear to be susceptible to a heat-induced loss of DNA-binding activity, with Ku80 representing the heat-sensitive component. Since the heat-induced loss and subsequent recovery of Ku-DNA binding activity correlates well with heat-radiosensitization, a role for Ku80 and NHEJ in heat-radiosensitization has been proposed. However, direct evidence implicating Ku80 (and NHEJ) in heat-radiosensitization has been indeterminate. In this study, we demonstrate that equitoxic heat treatments at 42.5-45.5 degrees C induce a similar amount of aggregation of Ku80 in human U-1 melanoma cells. These data suggest that the time-temperature-dependent relationship between heat lethality and Ku80 aggregation are similar. However, the aggregation/disaggregation of Ku80 and its transient or permanent inactivation is unrelated to heat-radiosensitization. When survival curves were obtained for irradiated or irradiated and heated Ku80(-/-) mouse embryo fibroblasts (MEFs) and compared with survival curves obtained for wild-type (WT) cells, we found that heat-radiosensitization was not reduced in the Ku80(-/-) cells, but actually increased. Thus, our findings indicate that Ku80 is not essential for heat-radiosensitization. Non-involvement of Ku-dependent or Ku-independent NHEJ pathways in heat-radiosensitization was confirmed by comparing clonogenic survival between DNA ligase IV-defective and WT human cells. Our data therefore implicate homologous recombination in inhibition of repair of radiation-induced DSBs and as a target for heat-radiosensitization.
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Affiliation(s)
- Joseph R Dynlacht
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
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19
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Zeng ZC, Jiang GL, Wang GM, Tang ZY, Curran WJ, Iliakis G. DNA-PKcs subunits in radiosensitization by hyperthermia on hepatocellular carcinoma hepG2 cell line. World J Gastroenterol 2002; 8:797-803. [PMID: 12378618 PMCID: PMC4656564 DOI: 10.3748/wjg.v8.i5.797] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the role of DNA-PKcs subunits in radiosensitization by hyperthermia on hepatocellular carcinoma HepG2 cell lines.
METHODS: HepG2 cells were exposed to hyperthermia and irradiation. Hyperthermia was given at 45.5 °C. Cell survival was determined by an in vitro clonogenic assay for the cells treated with or without hyperthermia at various time points. DNA DSB rejoining was measured using asymmetric field inversion gel electrophoresis (AFIGE). The DNA-PKcs activities were measured using DNA-PKcs enzyme assay system.
RESULTS: Hyperthermia can significantly enhance irradiation-killing cells. Thermal enhancement ratio as calculated at 10% survival was 2.02. The difference in radiosensitivity between two treatment modes manifested as a difference in the α components and the almost same β components, which α value was considerably higher in the cells of combined radiation and hyperthermia as compared with irradiating cells (1.07 Gy-1vs 0.44 Gy-1). Survival fraction showed 1 logarithm increase after an 8-hour interval between heat and irradiation, whereas DNA-PKcs activity did not show any recovery. The cells were exposed to heat 5 min only, DNA-PKcs activity was inhibited at the nadir, even though the exposure time was lengthened. Whereas the ability of DNA DSB rejoining was inhibited with the increase of the length of hyperthermic time. The repair kinetics of DNA DSB rejoining after treatment with Wortmannin is different from the hyperthermic group due to the striking high slow rejoining component.
CONCLUSION: Determination with the cell extracts and the peptide phosphorylation assay, DNA-PKcs activity was inactivated by heat treatment at 45.5 °C, and could not restore. Cell survival is not associated with the DNA-PKcs inactivity after heat. DNA-PKcs is not a unique factor affecting the DNA DSB repair. This suggests that DNA-PKcs do not play a crucial role in the enhancement of cellular radiosensitivity by hyperthermia.
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Affiliation(s)
- Zhao-Chong Zeng
- Department of Radiation Oncology, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
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20
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Guan J, Stavridi E, Leeper DB, Iliakis G. Effects of hyperthermia on p53 protein expression and activity. J Cell Physiol 2002; 190:365-74. [PMID: 11857452 DOI: 10.1002/jcp.10069] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Although p53 responses after DNA damage have been investigated extensively, p53 responses after heat shock, which exerts cytotoxic action by mechanisms other than direct induction of DNA damage, are less well characterized. We investigated, therefore, the effect of hyperthermic exposures on the levels and DNA-binding activity of p53. Experiments were carried out with U2OS and ML-1 cells, known to express wild-type p53 protein. Although heating at 41 degrees C for up to 6 h had only a small effect on p53 levels or DNA binding activity, exposure to temperatures between 42.5 and 45.5 degrees C caused an immediate decrease in protein levels that was associated with a reduction in DNA binding activity. This observation is compatible with a high lability of p53 to heat shock, or heat sensitivity of the pathway regulating p53 levels in non-stressed cells. When cells were heated to 42.5 degrees C and returned to normal temperatures, a strong p53 response associated with an increase in protein levels and DNA binding activity was observed, suggesting the production of p53-inducing cellular damage. At higher temperatures, however, this response was compromised in an exposure-time-dependent manner. The increase in DNA binding activity was more heat sensitive than the increase in p53 levels and was inhibited at lower temperatures and shorter exposure times. Thus, the pathway of p53 activation is itself heat sensitive and compromised at high levels of exposure. Compared to p53 activation after exposure to ionizing radiation, heat-induced activation is rapid and short lived. When cells were exposed to combined heat and radiation, the response observed approximated that of cells exposed to heat alone. Wortmannin at 10 microM inhibited p53 activation for up to 2 h after heat shock suggesting the involvement of wortmannin-sensitive kinases, such as DNA-PK and ATM. Heat shock causes phosphorylation of p53 at Serine-15, but there is no correlation between phosphorylation at this site and activation of the protein. The results in aggregate indicate p53 activation in the absence of DNA damage by a heat-sensitive mechanism operating with faster kinetics than radiation-induced p53 activation. The former response may induce pathways preventing other stimuli from activating p53, as heat-induced activation of p53 is dominant over activation of p53 by DNA damage in combined-treatment experiments. These observations suggest means for abrogating p53 induction after DNA damage with the purpose of potentiating response and enhancing cell killing.
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Affiliation(s)
- Jun Guan
- Department of Radiation Oncology, Kimmel Cancer Center, Jefferson Medical College, Philadelphia, Pennsylvania, USA
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21
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Abstract
XRCC5 (also known as Ku80) is a component of the DNA-dependent protein kinase (DNA-PK), existing as a heterodimer with G22P1 (also known as Ku70). DNA-PK is involved in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break (DSB) repair, and kinase activity is dependent upon interaction of the Ku subunits with the resultant DNA ends. Nuclear XRCC5 is normally extractable with non-ionic detergent; it is found in the soluble cytoplasmic fraction after nuclear isolation with Triton X-100. In this study, we found that heating at 45.5 degrees C causes a decreased extractability of XRCC5 from the nuclei of human U-1 melanoma or HeLa cells. Such decreases in extractability are indicative of protein aggregation within nuclei. Recovery of extractability of XRCC5 to that of unheated control cells was observed after incubation at 37 degrees C after heat shock. The decrease in extractability and the kinetics of recovery were dependent on dose, although the decrease in extractability reached a plateau after heating for 15 min or more. Thermotolerant U-1 cells also showed decreased extractability of XRCC5, but to a lesser degree compared to nontolerant cells. When a comparable initial reduction of extractability of XRCC5 was induced in both thermotolerant and nontolerant cells, the kinetics of recovery was nearly identical. The kinetics of recovery of the extractability of XRCC5 was different from that of total nuclear protein in nontolerant cells; recovery of extractability of XRCC5 occurred faster initially and returned to the level in unheated cells faster than total nuclear protein. Similar results were obtained for thermotolerant cells, with differences between the initial recovery of the extractability of XRCC5 and total protein being particularly evident after longer heating times. Heat has been shown to inactivate XRCC5. We speculate that inactivation of XRCC5 after heat shock results from protein aggregation, and that changes in XRCC5 may, in part, lead to inhibition of DSB repair through inactivation of the NHEJ pathway.
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Affiliation(s)
- B D Beck
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Okada S, Ono K, Hamada N, Inada T, Kubota N. A low-pH culture condition enhances the radiosensitizing effect of wortmannin. Int J Radiat Oncol Biol Phys 2001; 49:1149-56. [PMID: 11240258 DOI: 10.1016/s0360-3016(00)01429-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE The radiosensitizing effect of wortmannin on human tumor cells in a low-pH microenvironment was compared with that in a neutral-pH environment. METHODS AND MATERIALS A172 human glioblastoma cells, A549 human lung adenocarcinoma cells, and HMV-1 human melanoma cells were treated with 20 microM wortmannin 2 h before irradiation, and cell survival was examined. A low-pH microenvironment was simulated by exposing cells to low-pH culture medium for 24 h before wortmannin treatment. The effects of wortmannin on the repair of DNA double-strand breaks (dsbs) after 50-Gy irradiation in both low- and neutral-pH conditions were measured by pulsed-field gel electrophoresis. Expression of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) in low-pH conditions was also compared with that in neutral-pH conditions by Western blot analysis. RESULTS The radiosensitizing effect of wortmannin was greater in low-pH cultures than in neutral-pH cultures for all cell lines. The fast-rejoining component of DNA dsb repair was inhibited more strongly in low-pH than in neutral-pH conditions, although there was little difference in DNA-PKcs expression between groups. CONCLUSIONS The low-pH culture condition, which was designed to mimic the microenvironment of the central tumor mass in actively proliferating solid tumors, enhanced the radiosensitizing effect of wortmannin by inhibiting the fast-rejoining component of DNA dsb repair and by prolonging the retention of nonrejoined DNA dsbs.
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Affiliation(s)
- S Okada
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ami-machi, Ibaraki, Japan
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Tomita M, Suzuki N, Matsumoto Y, Hirano K, Umeda N, Sakai K. Sensitization by wortmannin of heat- or X-ray induced cell death in cultured Chinese hamster V79 cells. JOURNAL OF RADIATION RESEARCH 2000; 41:93-102. [PMID: 11037577 DOI: 10.1269/jrr.41.93] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Here we found that wortmannin sensitized Chinese hamster V79 cells to hyperthermic treatment at 44.0 degrees C as determined either by colony formation assay or by dye exclusion assay. Wortmannin enhanced heat-induced cell death accompanying cleavage of poly (ADP-ribose) polymerases (PARP). Additionally, the induction of heat shock protein HSP70 was suppressed and delayed in wortmannin-treated cells. Heat sensitizing effect of wortmannin was obvious at more than 5 or 10 microM of final concentrations, while radiosensitization was apparent at 5 microM. Requirement for high concentration of wortmannin, i.e., order of microM, suggests a possible role of certain protein kinases, such as DNA-PK and/or ATM among PI3-kinase family. The sensitization was minimal when wortmannin was added at the end of heat treatment. This was similar to the case of X-ray. Since heat-induced cell death and PARP cleavage preceded HSP70 induction phenomenon, the sensitization to the hyperthermic treatment was considered mainly caused by enhanced apoptotic cell death rather than secondary to suppression or delay by wortmannin of HSP70 induction. Further, in the present system radiosensitization by wortmannin was also at least partly mediated through enhancement of apoptotic cell death.
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Affiliation(s)
- M Tomita
- Department of Radiation Oncology, Graduate School of Medicine, University of Tokyo, Japan
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Ohnishi T, Komatsu K, Tauchi H, Wang X, Takahashi A, Ohnishi K, Shiba A, Matsumoto H. Brief communication: heat-induced accumulation of p53 and hsp72 is suppressed in lung fibroblasts from the SCID mouse. Int J Radiat Biol 2000; 76:711-5. [PMID: 10866294 DOI: 10.1080/095530000138385] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
PURPOSE To investigate how DNA-dependent protein kinase (DNA-PK) contributes to p53-dependent signal transduction after heat shock, thermosensitivity and accumulation of p53 and hsp72 after heat shock in lung fibroblasts derived from the SCID mouse were analysed. MATERIALS AND METHODS Thermosensitivity at 44 degrees C in colony-forming units and Western blot analysis of p53 and hsp72 were analysed. RESULTS The results indicated that (1) the thermosensitivity at 44 degrees C of SCID cells was higher than that of parental cells and (2) heat-induced accumulation of p53 and hsp72 was abolished and suppressed in SCID cells as compared with that in parental cells respectively. CONCLUSIONS The findings suggest that the catalytic subunit of DNA-PK may play an important role upstream of p53 and hsp72, which are possible determinants of cellular thermosensitivity.
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Affiliation(s)
- T Ohnishi
- Department of Biology, Nara Medical University, Kashihara, Japan.
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Matsumoto Y, Umeda N, Suzuki N, Sakai K, Hirano K. A gel-electrophoretic analysis for improved sensitivity and specificity of DNA-dependent protein kinase activity. JOURNAL OF RADIATION RESEARCH 1999; 40:183-196. [PMID: 10494149 DOI: 10.1269/jrr.40.183] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
DNA-dependent protein kinase (DNA-PK) is considered a critical enzyme in the repair and/or signal transduction of DNA double-strand breaks. DNA-PK activity has been mostly measured through "DNA-plus-minus" or "DNA-pull-down" procedures using synthetic peptide as substrate followed by filter-binding analysis, i.e. liquid scintillation counting of acid-insoluble radioactivity bound to phosphocellulose filter. Considering that non-specific phosphorylation of other cellular proteins in filter-bound acid-insoluble count could interfere with the detection of specific phosphorylation of peptide substrate, we examined the specificity and characteristics of these assay procedures by SDS gel-electrophoresis of the reaction mixture. The electrophoretic pattern showed phosphorylation in wide range of non-specific protein bands other than the specific substrate. The very low DNA-PK activity shown by murine L5178Y or FSA1233 cells was unambiguously detectable as the count in substrate band. Even following DNA-pull-down procedure, which would separate DNA-PK from most of other protein kinases, substantial amount of phosphorylation of other cellular proteins were still contaminated. Thus by selectively counting the particular bands, small amount of specific phosphorylation of peptide substrate was reliably quantified. These results indicated that the DNA-PK activity through filter-binding analysis was, as suspected, contaminated by non-specific phosphorylation of other cellular proteins and also that the gel-electrophoretic analysis would improve detectability of specific phosphorylation by DNA-PK of synthetic peptide substrate and, therefore, would improve the kinase assay in both sensitivity and specificity.
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Affiliation(s)
- Y Matsumoto
- Department of Radiation Oncology, University of Tokyo, Japan
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